As Herman Cain attempts to successfully negotiating his way through the first major scandal of this presidential cycle, the candidate finds himself in the harshest spotlight of his career -- in part because, until recently, both the media and his political opponents have largely ignored him.

"With this big bullseye on my back, you're going to hear a lot of bad information about me, but they if they can't find anything, they'll make it up. They've already started," Cain boasted last week, before the allegations of sexual harassment surfaced.

Now, Cain's changing tale of what happened is threatening to derail the enthusiasm behind the "Cain Train" -- and will likely bring further scrutiny to some of his earlier contradictory statements on issues like abortion and a proposed "electric" fence along the U.S.- Mexico border.

He did get some heat, for about 15 minutes, for his signature 9-9-9 tax plan, which he later changed to his 9-0-9 plan. (Now he refers to it as the original 9-9-9 plan.) He has also wavered on if or when the plan was amended to exempt the poorest Americans from paying income taxes.

For most of the campaign, Cain has been a positive, upbeat new face. A non-politician, he is uniquely able to criticize Washington and the current occupant of the White House. His upbringing and background resonates with voters who are looking for someone real in a field of politicians who have, by their very nature, made statements and taken stances that have been altered over time. Very few politicians can stand up with a perfect record on every issue.

Unfortunately for Cain, his evolving story on the harassment charges has opened the door for opponents and reporters to look more closely at his statements.

Cain's challenge now is to stay on message attacking President Obama on the economy, criticizing Washington, and pledging a simple way forward. And his ability to rescue his campaign from the onslaught of charges and speculation will hinge on his ability to keep his story straight.

"The thing that I think is going to convince people that my campaign is credible is the fact that if I make a mis-statement, I'm willing to retract it. If I made a mistake, I'm willing to admit I made a mistake," he said last week.

All the other candidates have faced attacks for their comments and stances. Now, as he leads the polls, Cain is finding out the hard way that keeping a consistent message and avoiding mistakes may be the best way to keep his campaign credible.